Before we get into the differences between these two products, we should mention that the term “sunblock” is a dated one, since the FDA no longer allows for its use on labels as the descriptor “may overstate the effectiveness of completely blocking UV rays and give consumers a false sense of reassurance,” explains Dr. Garshick.
As such, what was once called sunblock now falls into the sunscreen category—specifically mineral-based formulas. This is as opposed to chemical-based products, which is what most people mean when they say sunscreen. Confused? Read on.
The mineral-based stuff was once called sunblock because it works by creating “a physical barrier that reflects UV rays away from the skin,” says Dr. Marcus, adding that it “provides broad-spectrum protection…[and] starts to work immediately upon application.” That’s also why sunblock is known as “physical sunscreen.” The most common ingredients used in mineral-based sunscreen include titanium dioxide and zinc oxide. And because this formula “blocks” the suns rays from penetrating the skin, it is not absorbed by the skin and, thus, very often leaves behind a visible white residue.